The invention relates to molding elastomeric articles and particularly to molding such articles with reduced surface projections or "flash".
In molding elastomeric articles wherein the article is both cured and formed to its final profile in a mold, openings, holes or other like interruptions of the mold cavity wall result in the final article having surface projections or "flash" caused by flow or extrusion of elastomeric material into these openings during the molding operation. It is usually necessary to remove all or major portions of this flash from the article as a final finishing step in the fabrication of the article.
In molding pneumatic tires in typical molds containing upper and lower mold half sections, which separate to remove the articles, such mold flash commonly occurs along the tread periphery which corresponds to the mold section parting line. Projections can also occur on a tire surface at areas corresponding to the vent openings or holes within the mold which are to permit passage of unwanted air from the mold during the initial stages of the molding operation when the article is being formed against the mold cavity wall.
Also, in molds which utilize replaceable mold segments, such as tread and bead segments or "rings", mounted on the mold sections to form parts of the cavity wall, flash can form by elastomeric material flowing or extruding into the junctures or interfaces where the edges of such segments meet with adjacent edges of mold surfaces of the mold sections.
This flash can move deep into these interfaces and form a thermal barrier to proper heat transfer between segments and the mold sections.